The present invention relates to the gear train of electronic timepieces which are driven by a battery, the object being to produce timepieces of good quality and of substantially reduced size by improvement in the structure of the gear train.
Starting with the initial development of the electronic timepiece, striking progress has been made in the miniaturization of the time standard source and the electronic circuitry through progress in both circuit design and the manufacturing process. Through the utilization of these techniques it has been possible to realize electronic timepieces which are almost as thin as mechanical timepieces. However, although such electronic timepieces are relatively thin, the planar dimensions of such timepieces have been relatively great and it has hitherto been possible to miniaturize the electronic timepices in the planar direction only by eliminating the second hand or by suffering excessive deflection of the second hand.
In order to achieve an electronic timepiece which is small in all three dimensions, the gear train, the battery which provides energy to the gear train and the coil of the motor must be miniaturized and all of these elements must be brought close to the center of the timepiece. Especially important is reduction in the diameter of the fourth wheel and pinion which constitute the seconds wheel composite. Moreover, the transfer efficiency of the gear train must be improved so that the hands can be operated by a small torque and the shape of the coil must be such that it can be miniaturized.